Two Steps Retrieval¶
Important
Two Step Retrieval loads only a partial set of the related objects (default size of the retrieved related collection is 10). To load additional related objects, use the Relation Paging API .
With this approach a collection of related objects for a specific relation property in a parent object is retrieved from the server. The client application must know parent object's objectId
. The API loads a collection of related children for one property at a time. Child objects retrieved in paged sets, see the Relation Paging API sectionfor additional details.
Suppose the Person
table has a one-to-many relationship column friends
pointing to the Users
table. The code below retrieves related BackendlessUser
objects for a specific Person
object:
Prepare Backendless.LoadRelationsQueryBuilder:
var loadRelationsQueryBuilder;
loadRelationsQueryBuilder = Backendless.LoadRelationsQueryBuilder.create();
loadRelationsQueryBuilder.setRelationName( "friends" );
var parentObjectId = // removed for brevity
var friendsArray;
friendsArray = Backendless.Data.of( "Person" ).loadRelationsSync(
parentObjectId,
loadRelationsQueryBuilder );
friendsArray.forEach( function( friend ) {
console.log( friend.email );
});
var parentObjectId = // removed for brevity
Backendless.Data.of( "Person" ).loadRelations(
parentObjectId,
loadRelationsQueryBuilder )
.then( function( friendsArray ) {
friendsArray.forEach( function( friend ) {
console.log( friend.email );
});
})
.catch( function( error ) {
console.log( "server reported an error - " + error.message );
});
Prepare Backendless.LoadRelationsQueryBuilder:
var loadRelationsQueryBuilder;
loadRelationsQueryBuilder = Backendless.LoadRelationsQueryBuilder.create();
loadRelationsQueryBuilder.setRelationName( "friends" );
var parentObjectId = // removed for brevity
var friendsArray;
friendsArray = Backendless.Data.of( Person ).loadRelationsSync(
parentObjectId,
loadRelationsQueryBuilder );
friendsArray.forEach( function( friend ) {
console.log( friend.email );
});
var parentObjectId = // removed for brevity
Backendless.Data.of( Person ).loadRelations(
parentObjectId,
loadRelationsQueryBuilder )
.then( function( friendsArray ) {
friendsArray.forEach( function( friend ) {
console.log( friend.email );
});
})
.catch( function( error ) {
console.log( "server reported an error - " + error.message );
});